Aviation light signals

In the case of a radio failure or a plane not equipped with a radio, air traffic control will use a light gun to direct the airplane. The light gun has a focused bright beam and is capable of emitting three different colors: Red, white and green. These colours may be flashed or steady, and have different meanings to planes in flight or on the ground. Planes acknowledge the instruction by wiggling their wings, or simply moving the ailerons if on the ground.

	In Flight	On the Ground
Flashing White	N/A	Return to starting point
Steady Green	Cleared to land	Cleared for takeoff
Flashing Green	cleared to approach airport, or return to land	Cleared to taxi
Steady Red	Continue circling, give way to other aircraft	Stop
Flashing Red	Airport unsafe, do not land	Immediately taxi clear of runway in use
Alternating Red and Green	continue current action with caution
Blinking Runway Lights	vehicles, planes, and pedestrians immediately clear landing area in use